ProPto&reg; Anodized Black 40.5-49MM Step-Down Adapter Ring Stepping Ring 40.5MM Lens to 49MM Filter Size for Camera Canon Nikon Lens Side : 40.5mm/1.6" Filter Side : 49mm/1.93" Material : Metal Anodized matte finish to compliment your camera Allows you to use larger size filters on lenses with a smaller diameter thread. The first number is the size that screws into the lense, the second number is the filter size.